Generally speaking, a server chassis is mounted on a rack by means of a pair of slide rail assemblies in server systems. The slide rail assembly is usually in a form constituted by two or three sections of rails to carry the server chassis. The difference is that three-section rails have longer extension lengths to meet actual specific requirements.
Among the technologies of three-section rails, the engagement between rails or the synchronous movement between rails along an extending direction has been common developed technologies, which also means that such related technologies have already become specific operational and commercial requirements. For example, U.S. Pat. Nos. 7,413,269 B2 and 6,997,529 B1 disclosed the engagement between engaging blocks and engaging holes (or engaging grooves) to ensure the positioning between rails and the synchronous movement.